JPH059455Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a scavenging port for a uniflow two-stroke engine.

[Conventional technology]

The scavenging port of the Uniflow two-stroke diesel engine will be explained with reference to FIG. In the figure, 1 is a piston, 2 is a cylinder liner, and 3 is a scavenging port. When the piston 1 opens the scavenging port 3 at the end of the scavenging stroke, scavenging air flows through the scavenging port 3.
The remaining combustion gas in the cylinder is pushed out through an exhaust valve (not shown) and scavenges the inside of the cylinder. At this time, the perforation direction of the scavenging port 3 is eccentrically opened with respect to the center of the cylinder in order to simultaneously impart swirling speed to the scavenging air flow, improve charging efficiency, and improve combustion.
The scavenging port angle shown is given. If D is the diameter of a circle centered on the cylinder center that is in contact with the extension line in the θ direction, this D is called the swirl circle diameter. After the scavenging air flows into the cylinder from the scavenging port 3, it makes a swirling motion within the region between the scavenging air port 3 and the inner surface of the cylinder, and then flows upward into the cylinder while being diffused.

[Problem that the invention attempts to solve]

In the conventional example, in order to improve combustion by providing a strong swirling flow to the scavenging air, a large scavenging hole angle θ is given to the scavenging air port, and the swirl circle diameter of each stage D ₁ = D ₂
In the first conventional example where = D ₃ , as shown in FIG. 5, the scavenging air flowing in from the scavenging port flows upward while making a swirling motion between the swirl diameter D and the inner circumference of the cylinder. A large amount of residual gas remains in the center of the cylinder, as shown by the diagonal lines, and even after the scavenging stroke is completed, this residual gas is not removed, reducing scavenging efficiency and making it impossible to secure a sufficient amount of air necessary for combustion. I was getting used to it.

In the second conventional example for improving the scavenging efficiency, scavenging ports having multiple scavenging angles θ are combined as shown in FIG. The scavenging air flowing in from the upper scavenging port flows around the outer circumference of the cylinder, and the scavenging air flowing in from the lower scavenging port flows through the center of the cylinder. In other words, by setting (θ ₁ > θ ₂ > θ ₃ ) and (D ₁ >D ₂ >D ₃ ), the scavenging efficiency is attempted to be improved. The lower part 33 of the scavenging port, which is perforated in the opposite direction, opens only when the piston descends to the lowest position, and is immediately closed when the piston rises again. Therefore, the time during which the scavenging air with a small scavenging angle θ flows is shortened. As shown by diagonal lines in Fig. 6, the residual gas is removed quickly from the outer periphery of the cylinder, but the removal speed is still slow at the center. Constant scavenging hole angle θ ₁ = θ ₂
Although there is an effect of improving the scavenging efficiency rate compared to the case where = θ ₃ , a significant improvement is not obtained. In other words, the concept of the shape of the scavenging port in the prior art is to separate the scavenging air and residual gas and push them away one after another to perform the scavenging action. As the piston works, the scavenging air flows outward, which is fundamentally contradictory, and the critical level of scavenging efficiency has to decrease, and this property tends to become more pronounced as the piston stroke becomes longer. There is.

The purpose of the present invention is to provide a scavenging port for a uniflow two-cycle engine that can solve the problems of conventional devices, provide high swirling flow and scavenging efficiency, and achieve good combustion and high output.

[Means for solving the problem]

The scavenging port of the two-stroke engine according to the present invention has changed the conventional concept of separating the scavenging air, that is, separating the scavenging air and residual gas as much as possible and eliminating them by displacement action, and conversely stirs the scavenging air within the cylinder, so that some residual gas remains. Based on the idea of performing scavenging action while mixing with gas, the upper part of the scavenging port has a smaller scavenging port angle θ, and the lower part of the scavenging port has a smaller scavenging port angle θ.
By forming the scavenging port so that the scavenging air is large, a strong scavenging swirling flow and high scavenging efficiency can be obtained at the same time.

[Operation] The upper scavenging port makes the scavenging angle θ smaller, so the streamlines of the scavenging flow are evenly distributed upwards from the center of the cylinder to the outer periphery, but the scavenging angle θ increases toward the bottom, causing centrifugal force. As a result, only the cylinder's outer circumference rotates upward, and the scavenging air flow lines from the upper and lower parts interfere with each other, resulting in mixing of scavenging air and exhaust air due to turbulence. As a result, some of the residual gas remains in the scavenging air, but the scavenging air flow has a uniform upward flow distribution in the cylinder radial direction as a whole, and a strong swirling flow actually reduces the ability to remove the residual gas. be enhanced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

As shown in FIGS. 1 to 3, the scavenging ports 3 in FIG. In this example, 3
tier) are arranged. In addition, the scavenging ports 31 of each stage,
As shown in FIG. 1, 32 and 33 are continuous scavenging ports that communicate in the axial direction of the cylinder liner 2. Further, the perforation direction of the upper scavenging port 31 of the cylinder faces toward the center of the cylinder, and the perforation direction of the scavenging port deviates from the center of the cylinder as it goes downward to 32 and 33, and the scavenging port angle θ increases. ing. As a result, the third
As shown in the figure, the scavenging port angle θ ₁ of the scavenging ports 31 to 33
~θ ₃ and swirl circle diameter D ₁ ~D ₃ are θ ₁ < θ ₂ < θ ₃ ,
D ₁ < D ₂ < D ₃ .

Next, the operation of the above embodiment will be explained.

At the beginning of the scavenging stroke, the scavenging port 31 first opens, and the scavenging air forms a streamline upward evenly in the cylinder radial direction. Subsequently, when the scavenging port 32 is opened, the streamline of the scavenging air passing through the scavenging port 32 cannot enter inside the swirl circle D ₂ due to the action of centrifugal force, so it interferes with the streamline passing through the upper scavenging port 31. When the scavenging port 33 continues to open, as shown in FIG. Interference between wires occurs, causing disturbance and agitation. As a result, some of the residual gas is taken into the scavenging air flow and the purity of the scavenging air decreases, but overall the momentum of the strong swirling flow given to the lower scavenging air port 33 is maintained and the scavenging air flow upwards into the cylinder. is distributed almost uniformly in the radial direction of the cylinder, and the scavenging action is performed without forming a region where the residual gas is concentrated, improving the scavenging efficiency.

Also, the longer the engine stroke, the
Since the ratio of the diffusion mixing region near the scavenging port 3 to the total cylinder volume is reduced, the scavenging efficiency is greatly improved compared to the conventional example.

[Effect of idea]

Since the present invention is constructed as described above, during scavenging, the center-directed flow in the upper part of the cylinder liner and the tangential-directed flow in the lower part interfere with each other, disrupting the streamlines of the scavenging air and promoting mixing and agitation. As a result, high scavenging efficiency can be obtained, resulting in good engine combustion and high output and low fuel consumption.

[Brief explanation of the drawing]

Figures 1 to 4 are related to the present invention; Figure 1 is an external view of the scavenging port 3;
The figure is a configuration diagram of the vicinity of the scavenging port, Figure 3 is a cross-sectional view of Figure 2, Figure 4 is an explanatory diagram of the scavenging flow, and Figure 5 is a diagram showing the scavenging flow.
The figure is an explanatory diagram of the scavenging flow of the first conventional example, and Fig. 6 is an explanatory diagram of the scavenging flow of the first conventional example.
FIG. 2 is an explanatory diagram of a scavenging flow in a conventional example. 3...Scavenging port, 31...Upper scavenging port, 32
...Middle scavenging port, 33...Lower scavenging port, θ...
Scavenging port angle.

Claims (1)

[Scope of utility model registration request] In a two-cycle engine in which scavenging ports are bored in a cylinder liner at equal intervals in the circumferential direction and arranged in multiple stages in the axial direction of the cylinder liner, each of the scavenging ports is bored in a direction perpendicular to the axis of the cylinder liner. At the same time, the scavenging ports of each stage are communicated in the axial direction of the cylinder liner, and if the stage of the scavenging port near the top dead center of the piston is the upper part, and the stage on the opposite side is the lower part, the upper part is The direction of the center of the scavenging port is approximately toward the center of the cylinder,
A scavenging port for a two-stroke engine, characterized in that the scavenging port has a plurality of scavenging ports having angles θ such that the center of the scavenging port is oriented further away from the center of the cylinder as the scavenging port is located at a lower part of a cylinder liner.